Bleaching of gray cotton knit goods



2 5 2 9 9 CROSS ammmrgg f 23, 1964 s. M. mans 3,142,531

mm or can coma mmum um nu. a. 1961 COTTON KNIT GOODS "13935.1."4: OPT|CAL ADO, 1'0 mm: u! um FLUORESCENT '04-: alums PII u'rul BR|GHTEN ERmucous urn loc'r-loo'r 7 "A" up POLYALKOXY ALKANOL "1-" I PHENYL ESTERSURFACE 'ACTIVE WETTING AGENT COTTON KNIT GOODS Coniainin OpficalBrigh'rening Agem and Su ace Acrive werfing Agenr sauna 7W1, mum TO no225% sA'ruaA-nou COTTON KNIT GOODS lmpregnmed wirh Op'rical BrighfeningAgem and Surface Acfive werfing Agent mans: m OATH uo-aso MINUTE A00. TOum: up nu 2 2 run or Auuu We, Ta 1- an: "a uni (Aq) ADD. TO MAKE UP TNGM! PEI LITII.

WATER WAH I U IOU SODIUM IISULI'ITI WASH WATER WAH I BLEACHED COTTONKNIT GOODS OF HIGH BRIGHTNESS, INVENTOR HIGH ABSORBENCY, LOW STUART -RFLUIDITY AND SUBSTANTIALLY FREE OF mo'rss 5M TTORNEY United StatesPatent 3,142,531 BLEACHING 0F GRAY COTTON KNIT GOODS Stuart M. Rogers,Syracuse, N.Y., assignor to Allied Chemical Corporation, New York, N.Y.,a corporation of New York Filed Feb. 8, 1961, Ser. No. 87,761 2 Claims.(Cl. 8--11l) This invention relates to bleaching cotton knit goods andmore particularly to a new and improved method of bleaching to obtainbleached cotton knit goods having superior properties.

In the bleaching of cotton knit goods, there are certain propertiesdesired in the product bleached goods. One important property desired inthe bleached goods is high absorbency. Absorbency is a property of thegoods of absorbing or taking into the fibers certain liquids and liqudcompositions, for instance dyes. Absorbency is especially important inknit goods destined for dyeing inasmuch as the dyeability can beaffected by the absorbency, and the absorbency also determines thesuitability of the cotton goods for other uses. A second importantproperty desired in the bleached cotton goods is brightness, i.e.whiteness. It is usually desired that the bleached goods have a highbrightness, and the difiiculty in the prior art of obtaining highbrightness has generally been the material attack on and degradation ofthe goods due to drastic bleaching methods used for obtaining the highbrightness. A third important property desired is that the bleachedcotton goods have low fluidity, which is a measure of the degree ofdegradation of the goods caused by the bleaching. Lower fluidities areindicative of less degradative attack on the goods while higherfluidities show greater degradation of the goods. A fourth propertydesired, also deemed important, in the bleached goods is freedom frommotes. The product bleached cotton goods which are strived for are thosewhich exhibit all of these properties.

Cotton goods have been bleached by scouring the same at elevatedtemperature in a strongly alkaline scouring liquor, followed bybleaching the goods for a prolonged period of 7 hours hours or more.This securing and prolonged bleaching of the goods is objectionablebecause it may result in degradative attack on the goods and alsobecause of the prolonged time period required.

One object of the present invention is to provide a new and improvedmethod for bleaching cotton knit .goods to Obtain bleached cotton knitgoods of superior properties.

Another object of the invention is to provide a method for bleachingcotton knit goods to obtain bleached cotton knit goods of highabsorbency.

Another object is to provide a method for bleaching to obtain cottonknit goods of high absorbency, high brightness, low fluidity andsubstantially free of motes.

A further object is to provide a method for bleaching cotton knit goodsto high brightness, high absorbency, low fluidity and substantialfreedom from motes within a short bleaching time.

Additional objects and advantages will be apparent as the invention ishereafter described in detail.

Knowing the problems in the art, I tried a great many combinations ofdifferent chemicals and bleaching procedures in an effort to obtainbleached cotton knit goods having the four properties mentioned, viz.,high absorbency, high brightness, low fluidity and freedom from motes,but the results have been unsatisfactory with either zero or very lowabsorbency between 1 and 1.5 usually being obtained, and unsatisfactorybrightness usually in the middle 80s and lower as well as poor removalof motes from the goods also being obtained. I tried pretreating thecotton knit goods by immersing the same in 3,142,531 Patented July 28,1964 2 Y a sodium hexametaphosphate solution followed by washing thegoods and then bleaching the goods with peroxide solution containingsodium silicate stabilizer but the results were still unsatisfactorywith either no or low absorbency being obtained. I found that only byemploying the following combination method with observance of theproportions of ingredients in the wetting-out and bleaching compositionsas well as observance of the times and temperatures of the treatmentswas there attained bleached cotton knit goods of high absorbency as wellas high brightness, low' fluidity, i.e. no material degradative attackon the goods, and freedom or substantial freedom from motes. Inaccordance with the present invention, the cotton knit goods areimmersed in a bath of an aqueous wetting-out solution at a temperaturewithin the range 140 F.-l F., preferably 160 F.-l80 F. and containing0.5-5 grams per liter, preferably 0.5-l gram per liter of an opticalbrightening agent and -4, preferably 1.5-3 grams per liter of a wettingagent of the groups consisting of non-ionic and cationic surface activewetting agents. The goods are kept immersed in the bath for a time offrom about l-l0 minutes, preferably about 2-4 minutes at temperaturewithin the aforesaid range and the goods are preferably stirred while inthe bath. Then, without rinsing the goods, the goods are squeezed to aISO-225% saturation, preferably 175-20092; saturation, followed byimmersing the goods in an aqueous alkaline hydrogen peroxide bleachingsolution free of alkali metal silicate, preferably an aqueous hydrogenperoxide solution containing from about 7-10, preferably 8-9 grams perliter of hydrogen peroxide, from about 1-6, preferably 3-4 grams perliter of sodium hydroxide and preferably also borax (Na B O in amountfrom about 0.5-2, preferably l-1.5 grams per liter. The goods are keptimmersed in the peroxide bleaching solution at a temperature within therange l60-2l0 F., preferably 170-l90 F., for a period of about 250-350minutes, preferably about 280-320 minutes, and the goods are then washedwith water, preferably first washed with hot water, then with coolwater, thereafter with aqueous sodium bisulfite solution and again withwater.

In a specific embodiment of the invention, the cotton knit goods areimmersed in a bath of an aqueous wettingout solution having a preferredconcentration of 0.5-1 gram per liter of an optical brightening agentand 1.5-3 grams per liter of an anionic or non-ionic surface activewetting agent. A concentration below 0.5 gram per liter of the opticalbrightening agent would not be effective, and it would be unnecessary toemploy concentrations of optical brightening agent above about 5 gramsper liter inasmuch as these higher amounts would give no better resultsand may be undesirable from an economic standpoint. The wetting-out bathis at preferred temperature of about -180 F. and the goods are keptimmersed in the bath for preferably about 2-4 minutes at temperaturewithin the above disclosed range, the goods being preferably stirredWhile in the bath. The goods should be maintained in the bath for atleast about 3 minutes to insure obtainment of the high brightness andhigh absorbency in the final bleached product, and it is unnecessary tohold the goods in the bath for more than about 10 minutes inasmuch aslittle, if any, advantage is gained thereby.

Optical brightening agents are known materials, commercially available,and marketed as Leucophor BS (Sandoz Co.) or Calcofiuor White ST(American Cyanamid Co.) which is4,4'-bis(4-anilino-6-diethanolamines-triazin-2-ylamino)-2,2'-stilbenedisulfonicacid, disodium salt. Surface active wetting agents, well-knownmaterials, are commercially available, of the non-ionic and anionic typeand include polyalkoxy alkanol phenyl esters,

3 for instance isooctyl phenyl polyethoxy ethanol (Triton X-IOO), andsodium alkyl aryl sulfonate (Alkanol WXN").

After the wetting-out treatment, the goods are removed from the bath andwithout rinsing, the goods are squeezed to a 175-200% saturation, whichis a goods-solution ratio of 1:1.75-112. The goods are then placed in akier and an aqueous alkaline peroxide bleaching solution is added to thekier so that the goods are immersed in the bleaching solution. Theperoxide bleaching solution is free of sodium silicate decompositionstabilizer or other alkali metal silicate, and preferably is an aqueoushydrogen peroxide solution containing from about 7-10 g.p.l. hydrogenperoxide, about 1-6 g.p.l. sodium hydroxide and preferably about 0.5-2g.p.l. borax (Na B O Use of the aqueous peroxide bleaching solutiondevoid of alkali metal silicate in accordance with the inventionresulted in bleached cotton goods having an excellent absorbency as wellas a high brightness. The peroxide bleaching solution is preferably attemperature of about 160- 180 F., and the pH of the peroxide solutionmay be within the range of pH 8-12, preferably pH 10-11 by virtue of thesodium hydroxide. The goods are held in the peroxide bleaching solutionfor a time of preferably about 280-320 minutes.

The thus-treated goods are then washed with water, preferably first withhot water, then with cool water, thereafter with aqueous sodiumbisulfite solution and again with water. The washed goods may then besqueezed or pressed and dried.

The brightness of the bleached cotton knit goods was determined using astandard General Electric reflectometer. A G.E. brightness of 86% orabove is considered good for cotton goods.

The absorbency of the cotton knit goods is determined by the followingprocedure. /2-ll'lCh strips of the cotton goods are fastened withoutstretching between prongs projecting from the edge of two disks, spacedabout 6 inches apart by means of a supporting rod passing through thecenter of each disk. The assembly is then placed in a vertical glasscylinder containing l-lMz inches of distilled water. At the end ofminutes as determined by a stopwatch started simultaneously with placingthe assembly in the cylinder, the height of the water absorption in thecotton strips is measured by means of a transparent scale attached tothe outside of the cylinder by flexible bands. The zero point isadjusted to the water level and each i -inch rise of water in the fabricis equivalent to 1 point of absorbency. The absorbency test is carriedout at 73 F. and a relative humidity of 50%. An absorbency of 25-30 isacceptable and absorbency above 30 is rated excellent.

Degradation or modification of the cotton fibers due to the chemicalsused in the processing is very effectively and accurately measured bydetermining the fluidity of the cotton cellulose dissolved incuprammonium hydroxide according to standard procedure. The fluidityvalues attached are largely independent of the fabric construction, andthe test is a very useful one inasmuch as the degradation of the fiberscan be used to predict the effect of chemical treatments on the tensilestrength of the fabrics and their wearing qualities. The fluidity valuesare measured in rhes, i.e. reciprocal poises, with values about 6indicative of the degradation of the cotton fibers and values below 4indicating superiod strength of the fibers. The mote content wasdetermined by careful visual inspection of the cotton knit goods.

The following comparative examples illustrate the invention.

Example I A 50 gram sample of gray tubular cotton knit goods wasimmersed and stirred for 3 minutes at 180 F. in 500 ml. of an aqueoussolution containing 3.0 g.p.l. of an isooctyl phenyl polyethoxy ethanol(Triton X-100") and 0.69 g.p.l. Calcofluor ST White" solution(4,4'-bis(4- anilino-6-diethanolamine-s-triazin-2-ylamino) 2,2stilbenedisulfonic acid, disodium salt) brightener. Without washing, thegoods were squeezed to a 200% solution saturation and piled in a glasskier. 60 ml. of an aqueous solution containing 8.75 g.p.l. H 0 1.0g.p.l. Na B O and 3.0 g.p.l. NaOH and 10 cc. of water were added to thekier, circulated and heated to F. and held for 5 hours. The kier wasdrained and the sample given 5- minute circulating rinses with separateportions of hot water, cool water, 2.0 g.p.l. NaHSO and 0.7 g.p.l. NaHSOafter which the goods were removed from the kier and washed. The goodswere then cut into pieces of about equal size which were placed betweenblotters to remove water, then pressed at 600 lbs. p.s.i. between freshblotters and dried. The results of this run were:

Brightness 90.1. Fluidity 1.9 Absorbency 61.

Mote removal Excellent.

Example II The procedure of Example I was repeated but the isoocetylphenyl polyethoxy ethanol of the pretreatment wetting-out solution wasreduced to 0.75 g.p.l. in the wetting-out solution of Example I. Theresults obtained were:

Brightness 88.5. Fluidity 1.8. Absorbency 52.

Mote removal Excellent.

Example III The procedure of Example I was followed except that thepretreatment wetting-out solution contained no isooctyl phenylpolyethoxy ethanol or other wetting agent. The results obtained were:

Brightness 85.1. Fluidity 2.3. Absorbency O.

Mote removal Excellent.

Example IV The procedure of Example I was repeated except that theaqueous peroxide bleaching solution contained 3.0 g.p.l. Na B O Theresults obtained were:

The procedure of Example I was repeated except that the aqueous peroxidebleaching solution contained no Na B O The results obtained were:

Brightness 88.1. Fluidity 1.9. Absorbency 60.

Mote removal Excellent.

Example VI The procedure of Example I was repeated except that theaqueous peroxide bleaching solution contained 4.0 g.p.l. NaOH. Theresults obtained were:

Brightness 90.8. Fluidity 1.9. Absorbency 61.

Mote removal Excellent.

Example VII The procedure of Example I was repeated except that theaqueous peroxide bleaching solution contained 5.0 g.p.l. NaOH. Theresults obtained were:

The procedure of Example I was repeated except that the aqueous peroxidebleaching solution contained no NaOl-l. The results obtained were:

Brightness 85.2. Fluidity 2.1. Absorbency 53.

Mote removal Poor.

The efiective bearing of the concentration of wetting agent of thewetting-out solution is readily apparent from the above examples. Whenthe amount of this wetting agent was lowered to 0.75 g.p.l. in Example11 a marked drop in absorbency from 61 to 52 took place as well as asignificant decrease in brightness. Omission of the wetting agent fromthe wetting-out solution of Example 111 resulted in zero absorbency andcaused the brightness to decrease further. The effect of omitting NaOHfrom the peroxide bleaching solution is readily apparent from theresults of Example VIII in which the mote removal was poor and thebrightness was materially lowered.

The present invention not only achieves a good brightness for the cottongoods but also achieves good results with respect to 3 additionalproperties of the goods which the prior art has found to be difficult toachieve with respect to all four properties simultaneously. Cotton knitgoods processed in accordance with the invention not only ischaracterized by higher absorbency but in addition by having a higherbrightness, lower fluidity, i.e. less degradation of cellulose fibersand considerably improved mote removal.

Although certain preferred embodiments of the invention have beendisclosed for purpose of illustration, it will be evident that variouschanges and modifications may be made therein without departing from thescope and spirit of the invention.

A flow diagram of the inventive bleaching process is shown in theattached drawing.

I claim:

1. A method for bleaching gray cotton knit goods which consists ofimmersing the gray cotton knit goods in a bath of an aqueous solutionconsisting of 0.5- grams per liter of an optical fluorescent brighteningagent and 1.25-4 grams per liter of a polyalkoxy alkanol phenyl estersurface active wetting agent at a temperature within the range 140F.-l90 F., keeping the goods immersed in said aqueous solution bath fora time of from about 1-10 minutes at temperature within the aforesaidrange, then directly squeezing the goods to a -225 saturation, thenimmersing the squeezed goods in an aqueous alkaline hydrogen peroxidebleaching solution consisting of 1-6 grams per liter of sodiumhydroxide, about 7-10 grams per liter hydrogen peroxide and from about0.5-2 grams per liter, keeping the goods immersed in said peroxidebleaching solution at a temperature within the range F.-210" F. for aperiod of from about 250-350 minutes, removing the goods from theperoxide bleaching solution and water washing, then treating the goodswith dilute aqueous sodium bisulfite solution, and washing thethus-treated goods with water to obtain cotton knit goods of highbrightness, high absorbency, 10w fluidity, and substantially free ofmotes.

2. A method for bleaching gray cotton knit goods which consists ofimmersing the gray cotton knit goods in a bath of an aqueous solutionconsisting of 0.5-1 gram per liter of4,4'-bis(4-anilino-6-diethanolamino-s-triazin-Z-ylamino)-2,2-stilbenedisulfonic acid, disodium salt opticalfluorescent brightener and 1.5-3 grams per liter of a polyalkoxy alkanolphenyl ester surface active wetting agent at a temperature within therange of 160 F.- F., keeping the goods immersed in said aqueous solutionbath for a time of from about 2-4 minutes at temperature within theaforesaid range and stirring the goods while in the bath, then directlysqueezing the goods to a 175-200% saturation, then immersing thesqueezed goods in an aqueous alkaline hydrogen peroxide bleachingsolution consisting of from about 7-10 grams per liter hydrogenperoxide, from about 3-4 grams per liter sodium hydroxide and from about0.5-2 grams per liter borax, keeping the goods immersed in said peroxidebleaching solution at a temperature within the range of 170 F.- F. for aperiod of from about 280-320 minutes, removing the goods from theperoxide bleaching solution and water washing, then treating the goodswith dilute aqueous sodium bisulfite solution, and washing thethustreated goods with water to obtain cotton knit goods of highbrightness, high absorbency, low fluidity and substantially free 'ofmotes.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Furry et al.: Proc. Am. Assoc. Tex. Chem. and Colorists, 44(23), pp. 786-790, Nov. 7, 1955. (Patent Ofiice Scientific Library.)

Teintex: (1941), No. 6, pp. English in Div. 43 relied upon).

222-226 (abstract in UNITED STATES PATENT OFFICE CERTIFICATE J OFCORRECTION Patent No, 3 142531 July 28 1964 Stuart M Rogers It is herebycertified that error appears in the above numbered patent requiringcorrection and that the said Letters Patent should read as correctedbelow.

Column 1, line 42, strike out "hours" second occurrence; column 3 line38 after "projecting" strike out the dash; line 65. for "superiod" readsuperior column 6, line 7 after "liter" insert borax '--q Signed andsealed this 17th day of November 1964.,

(SEAL) Attest:

ERNEST W. SWIDER' EDWARD J. BRENNER Attesting Officer Commissioner ofPatents UNITED s-rATE-s PATENT OFFICE GERTIFIGATE 0F CORRECTION PatentNo, 3 142531 July 28 1964 I Stuart M Rogers It is hereby certified. thaterr ent requiring correction and that th or appears in the abovenumbered patcorreeted'b'elow.

e said Letters Patent should read as Column 1 line 42 strike out"hoursfi, column 3,, line 38,, after line 65,, for "superiod" 7,, after"liter" insert second occurrence; projecting" strike out the dash;

read superior column 6,, line borax 'Q Signed and sealed this 17th dayof November 19641o (SEAL) Attest:

Commissioner of Patents

1. A METHOD FOR BLEACHING GRAY COTTON KNIT GOODS WHICH CONSISTS OFIMMERSING THE GRAY COTTON KNIT GOODS IN A BATH OF AN AQUEOUS SOLUTIONCONSISTING OF 0.5-5 GRAMS PER LITRE OF AN OPTICAL FLUORESCENTBRIGHTENING AGENT AND 1.25-4 GRAMS PER LITER OF A POLYALKOXY ALKANOLPHENYL ESTER SURFACE ACTIVE WETTING AGENT AT A TEMPERATURE WITHIN THERANGE 140*F.-190*F., KEEPING THE GOODS IMMERSED IN SAID AQUEOUS SOLUTIONBATH FOR A TIME OF FROM ABOUT 1-10 MINUTES AT TEMPERATURES WITHIN THEFORESAID RANGE, THEN DIRECTLY SQUEEZING THE GOODS TO A 150-225%SATURATION, THEN IMMERSING THE SQUEEZED GOODS IN AN AQUEOUS ALKALINEHYDROGEN PEROXIDE BLEACHING SOLUTION CONSISTING OF 1-6 GRAMS PER LITEROF SODIUM HYDROXIDE, ABOUT 7-10 GRAMS PER LITER HYDROGEN PEROXIDE ANDFROM ABOUT 0.5-2